The invention is concerned with the photodynamic diagnosis of tumor tissue and relates in particular to a device for the photodynamic endoscopic diagnosis of tumor tissue in the human or animal body with the help of a marker substance capable of fluorescence and with an endoscope as well as a light source. With this there are provided means in order to guide light from the light source via the endoscope to the diagnosis location in each case in one of at least two selectable spectral regions, that is the white light region and a region with blue-violet light, and in each case to be able to carry out a visual examination with white light and to stimulate a marker substance accumulated in any tumor tissue, to fluoresce.
With such a known device for tumor examination, a patient receives a systematic, oral, topical, instilled or otherwise enriched dosage of the dye .delta.-amino levulinic acid (ALA). After a given reaction time the body converts this substance into the dye porphyrine IX (PP IX). This preferably deposits itself in the regions changed by disease (DE 42 28 106 A). On illumination of the surface of the organ with light of a suitable spectral combination, the regions having a high PP IX concentration fluoresce with a red color and thus permit an easy detection and spacial definition of the diseased region.
The light which is suitable for stimulating PP IX contains only spectral components of approximately 380 to 445 nm, appears intensive blue-violet to the eye and thus is not very suitable for a normal diagnosis or for spacial orientation, e.g. in the body cavity to be examined, since it is desirable, before the diagnosis supported by fluorescence, to carry out a diagnosis under white light and to repeat this where appropriate. This means that the examining surgeon must be able to choose between these two operating types.
However by way of the intensive illumination of the surface of the organ the dye is broken down relatively quickly in the accumulation regions, by which means the fluorescence intensity is reduced and eventually completely disappears. This process is called "fading". Fading however occurs not only with illumination with blue light, i.e. in the blue light mode, but also with illumination with white light, in the white light mode, since the white light likewise contains fluorescence stimulating spectral components. With examination with white light the time thus available for an effective fluorescence diagnosis is reduced. Since the examination with white light is generally carried out first of all, it may even occur that the dye, i.e. the marker substance, has already faded before the first actuation of the actual stimulation light, due to which the flourescence supported diagnosis is no longer possible.
Moreover in some cases with the fluorescence examination in the blue light mode, the tumor does not distinguish itself clearly enough or unambiguously from healthy tissue. In such cases an increase in the contrast would be desirable.
From DE 196 08 027 A1 there is known a device for the photodynamic endoscopic diagnosis of tumor tissue. The examination is carried out with the known device in two operating modes, that is in the white light mode and in the blue light mode, however this is without a marker substance being led to the patient. In the light source there is located a stimulation light filter which only lets through light in a narrow wavelength band of 420 to 480 nm in order to be able to carry out a fluorescence observation on cancerous tissue with an endoscope. With observation in the white light region, this stimulation light filter is removed from the light path. To the endoscope there can be connected a televison camera unit which comprises a normal camera for taking a normal observation picture, i.e. in the white light region, and a fluorescence camera for taking a fluorescence picture. An optical system in the television camera unit contains a filter, for the fluorescence observation, which is arranged in front of the imaging lens, blocks off light with wavelengths which are let through by the stimulation light filter, and which only lets through light with wavelengths greater than 480 nm and smaller than 520 nm. Therefore only this light can reach the image intensifier of the fluorescence camera.
For producing fluorescent light, when biological tissue is illuminated with light in the region of 470 to 480 nm, this known device works in the region of the dimensional order of 480 to 600 nm with an intensity peak of 480 to 520 nm, wherein however cancerous tissue or other diseased tissue does not fluoresce. If the stimulation light filter is located in the beam path then only the fluorescing light produced by normal tissue of the object reaches the image intensifier of the fluorescence camera and is correspondingly intensified. Thus, because the device known from DE 196 08 027 A1 does not use a marker substance for marking the tumor tissue, the problem of fading of the marker substance does not occur.
DE 195 12 518 A1 describes an apparatus for treating tumors comprising a light source which emits a bundle of rays with ultraviolet, visible and infrared radiation. An infrared filter as well as a filter for visible radiation are arranged in front of a light guide which directs the filtered bundle of rays onto an affected tissue part. For treatment, the patient is enriched with Ti02 (titanium dioxide) which accumulates much more in tumor cells. Thus when the tumor cells are irradiated with electromagnetic waves of a wavelength from the X-ray region to ultraviolet, with this the Ti02 is stimulated so that the tumor cells are destroyed by the released active oxygen. Apart from the fact that the apparatus known from DE 195 12 518 A1 is used for the treatment and not the diagnosis of tumors, in none of the operating modes is a protective filter employed. The region which stimulates the Ti02 in the tumor cells (approx. 280 to 400 nm) is always completely let through.